Characteristics and key points of the most popular

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Features and process points of self-adhesive trademark printing

self adhesive trademark is mainly to meet the needs of convenient pasting of commodity brand labels. A layer of self-adhesive layer is evenly coated on the back of the paper and adhered to a layer of wax coated paper that is easy to peel off. There are two kinds of self-adhesive, roll type and sheet type. The commonly used self-adhesive trademark is a kind of printed matter with a certain shape left on the waxed paper by rolling and cutting with a knife line after printing, stripping the blank excess part. When in use, as long as the finished product is peeled off and pasted directly on the commodity or package, it is very convenient and fast. In addition to coated paper and other paper, self-adhesive trademarks also include self-adhesive prints with aluminum foil, gold card, silver card and color polyester film as substrates

I. characteristics of self-adhesive printing

our factory often uses four open and eight open offset printing machines to print self-adhesive trademarks, packaging and decoration products. The differences between self-adhesive printing and other printing methods:

1. The self-adhesive paper is relatively thick, which generally has the thickness of two 150g/m2 coated paper. It is composed of coated paper, aluminum foil, color polyester film substrate and wax paper layer

2. The self-adhesive printing paper is generally high-grade coated paper, gold card, silver card paper and colored polyester film, and the surface of the paper is smooth and bright

3. Self adhesive paper has low ink absorption

4. It is easy to get dirty on the back when printing full-scale field images

II. Several points that should be paid attention to in self-adhesive printing

1. Adjust the printing pressure. In the process of offset printing, each of the adjacent two rollers of the three rollers of printing plate, rubber and impression is in contact with each other and squeezed to play the role of transfer printing. In order to get normal ink transmission on the printing paper and truly reproduce the continuous tone words, lines, images and halftone points of the graphic part, in addition to the contact between the two roller surfaces, these impressions must be additionally subjected to the necessary printing pressure. The weight of the printing pressure and the accuracy of the adjustment will directly determine the size, depth and quality of the ink in the image and text transfer and the reproduction of the printing point. It is necessary to adjust the center distance between the impression cylinder and the rubber cylinder during self-adhesive printing, and the center distance of the cylinder can be increased by about 0.2 ~ 0.4mm. If the paper becomes thinner from thick, the reduced thickness, that is, the lining thickness removed from the plate liner, should be added to the rubber drum; If the paper turns from thin to thick when printing, subtract a certain thickness from the rubber cylinder liner, and add the corresponding thickness to the liner of the plate cylinder

during plate loading, it is necessary to compress and compact to prevent the operation from sliding relatively during printing. In practice, the ideal printing pressure is generally controlled at 0 About 25mm, it must be emphasized that the ideal printing pressure is to make the imprint of the graphic part of the printing plate strong enough on the paper under a certain compression deformation of the printing surface, and use the minimum pressure on the basis of clear and complete points

2. Pay attention to the adjustment of the paper feeding part when printing self-adhesive. The air volume of the paper suction nozzle and the paper blowing nozzle of the paper feeding part should be increased accordingly

3. The paper separating suction nozzle and the paper feeding suction nozzle should be replaced with rubber bands with larger diameter and thickness to achieve the purpose of stable paper feeding and no swing of the paper feeding roller

4. Due to the thickness of two layers of coated paper, the paper thickness should pay attention to the gap of the double sheet controller should also be increased in line with the improvement of industrial competitiveness. The distance between the paper pressing tongue of the side gauge and the front gauge and the paperboard should be increased

5. The distance between the paper feeding tooth pad and the surface of the embossing cylinder, as well as the electro-hydraulic servo valve between the paper feeding tooth pad and the paperboard conveying has the advantages of fast dynamic response, high control accuracy, long service life and so on, should be increased, and the distance should be kept about equal to the paper thickness plus 0.3mm

III. arrangement of color sequence of self-adhesive printing

1. Self adhesive printing products have full page field, as well as words, lines and patterns. For example, for printing products such as wine boxes and drug trademarks, the color sequence of printing is best to first print words, lines and patterns, and then put the full version on the ground for final machine printing, so as to avoid the phenomenon that the paper collides and rubs with each other and the back is sticky and dirty when the imprint is not dry due to the thickness of the self-adhesive paper

2. Print the dark color on the front and the lighter color on the back. Because the ink with darker color has strong hiding power and strong adhesion, print it first on the front, which is convenient for accurate overprint. The hiding power of the light color is weak. It is difficult to observe when overprinting it on the back. Correspondingly, the effect of overprint is good

3. Often in a printing product, there are halftone four-color electric separation points, as well as continuous tone patterns, words and lines. At this time, the electric separation four-color points should be printed first, which is conducive to accurate overprint and reduce the influence of paper expansion, and then continuous tone words, lines and plans should be printed. In the arrangement of printing color sequence, we should recognize the primary and secondary, and it is more appropriate to be difficult first and then easy

4. In summer, the weather changes greatly, and in rainy seasons, the temperature and humidity of the environment should be well controlled, which will affect the uneven water content and wrinkling of self-adhesive printing paper; The paper stack and semi-finished products cut out should be tightly wrapped with plastic before and after printing

IV. how to prevent the self-adhesive printing from getting dirty

l. The self-adhesive is easy to get dirty on the back when it is printed on the full plate. Because the ink absorption of coated paper on the surface of the self-adhesive is poor, try to use the original barrel of ink when printing, do not add 6# ink mixing oil, and add some de adhesion agent and anti adhesion agent appropriately; Do not add dry oil when the weather is hot. It is often easy to get dirty on the back of the full plate on the ground, and it is often solved by spraying powder. Although the printing anti sticking dirty powder spray contains pure vegetable materials, and its dispersibility and fluidity are good, the use of powder spray will directly affect the surface gloss of printing products, make the ink not bright, pollute the environment, and also affect the accuracy of offset printing machines

2. Pay attention to the balance of offset printing ink and water, and control the water content of the printing page. On the premise that the printing plate is not dirty, use the minimum amount of water in the plate. The self-adhesive is smooth and bright. When printing the full plate on the ground, first print the dark color, and the ink volume is enough, subject to the fact that the back is not sticky and dirty, and then print the background color thinly. The smoothness of such printing products will be better before and after the accident

3. Overcome the disadvantages of large water and ink in offset printing. The ink cannot be adjusted too thin. If it is too thin, it is easy to get dirty on the back. If it is too thin, some new ink can be added to enhance the viscosity of the ink

v. self adhesive printing and pasting roller and multiple cards

self adhesive is evenly coated with a layer of self-adhesive layer on the back of the paper and adheres to a layer of wax coated paper that is easy to peel off. In summer, when it is hot and the temperature is high, the adhesive under the roller between the rollers will leak out of the paper gap, and a small amount of adhesive will flow out under the high temperature and the pressure of the mechanical roller, sticky and connected, It will directly affect the accurate overprint of normal paper feeding. The self-adhesive liquid at the edge of the paper will be pasted on the rubber drum, which is easy to stick the self-adhesive on the drum, ink roller and embossing drum for trial production and safety and health control project testing, commonly known as "wrapping". This is one of the biggest drawbacks of self-adhesive in printing. In the actual work of offset printing, we encounter the solution to this kind of situation: after the self-adhesive is cut and before the offset printing, talcum powder and plant starch (anti sticking and dirty spray powder) should be coated on the side and around the cut of the self-adhesive, so that the self-adhesive liquid can be wiped off and covered, so as to avoid the defects of self-adhesive flow caused by roller pressure and weather, and the effect is very good

for self-adhesive printing, because the paper is thick, multiple sheets of self-adhesive are blocked into the embossing and rubber drum, which is easy to cause "stuffy car", so before starting printing, we must carefully adjust the double sheet control, skew control and other electrical devices appropriately. During double sheet control, the distance between the double sheet control wheel and the paper feed roller should not be less than two sheets of paper, but should not be greater than three sheets of paper, otherwise the curved paper will stop when it passes through the controller; Or the double sheet has passed through the controller, and the two contacts of the controller power supply have not been contacted, so the purpose of controlling the double sheet cannot be achieved. When working, the dust, dirt or insulation on the surface of the double sheet control wheel and the paper feed roller, or on the surface of the two contacts at the power control, should be cleaned in time to prevent the failure of the double sheet control system, the occurrence of paper jam and the failure of the rubber roller and the embossing roller. (author: Wang Xincheng)

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